This invention relates to the lubrication and cooling of a thrust bearing in a vertical electric motor.
It is well known to use various types of heat exchanger apparatus to maintain a lubricant, which is in heat absorbing contact with the heat-generating thrust bearing of a vertical electric motor, within a safe operating range of temperatures. Air cooled heat exchangers are frequently used when the size of the electric motor is such that relatively little heat is dissipated from the thrust bearing into the lubricant, and water cooled heat exchangers are used for the lubricant in larger motors which use thrust bearings that generate significantly more heat. In one known air cooled heat exchanger structure the lubricant is contained within a cylindrical reservoir, or well, surrounding the thrust bearing above the top end frame and having hundreds of open-ended pipes sealed to the top and bottom walls of the well, and ambient air is drawn through the pipes to cool the lubricant. Such air cooled heat exchanger apparatus is expensive to construct because of the large number of pipes and also often results in leaks of lubricant at the seals to the pipes in the bottom wall of the reservoir into the interior of the motor housing. Further, the heated air circulating through the pipes enters the interior of the motor housing and makes cooling of the rotor and stator difficult. Another type of heat exchanger is a liquid-to-liquid heat exchanger for the lubricant. This type uses cooling tubes submerged in the lubricant through which water is circulated, and such water cooled heat exchangers require water inlet and water outlet pipes to external pumping equipment which prevent the lubricant cooling means from being self-contained within the motor enclosure. Such water cooled heat exchangers utilize mechanical moving parts in the pumping apparatus which are subject to wear as well as water circulating pipes between the motor enclosure and the installation site which are subject to contamination, corrosion and breakage with the result that such heat exchangers are inconvenient, complex, costly to manufacture and to maintain, and unreliable when subjected to mechanical stresses encountered in earthquakes or similar upheavals.